Blood clot (thrombus), generated in blood vessels (arteries or veins), by activation of blood coagulation cascade and culminates in the generation of thrombin at the site together with platelet aggregation, resulting in formation of a blood clot composed of platelets and fibrin. The coagulation process of the blood clot involves charged proteins, enzymes, phospholipids and mineral ions, and platelets. Therefore, electrostatic forces may act on the clot by these components, protein enzymes activity and structural conformation changes. It was shown in previous experiments by Sawyer [P. N. Sawyer, et al., “Electrical Hemostasis in Uncontrollable Bleeding States”, Annals of Surgery 154 (4) October 1961] that the positive electrode of a direct current electrode pair applied to the surface of a blood vessel can produce thrombosis that is attached to the positive electrode.
Various examples for using electrodes in blood vessels and other body passages or organs are known from the patent literature.
U.S. Pat. No. 4,027,674 describes a method and device for removing concretions within human ducts. The catheterization device used in this patent comprises an axially positioned flexible positive electrode together with a flexible negative electrode which are adapted for applying high voltage pulses with low currents for removing concretions from the urinary tract or the kidney. While this arrangement can be used for urinary tract treatments the pulse shape and amplitude suggested are too energetic for clot dissolution in blood vessels, and thus not suitable for such applications.
US Pat. No. 6,210,404 describes a design for producing energy power (heat) micro-catheter system to be delivered into a thrombus by generating acoustic waves due to high repetition rate of expansion and collapse of media. This design is based only on electro-thermal or electro-mechanical effects, and it aims to disassociate the thrombus by the acoustic waves traveling from the catheter site into the thrombus. This system relies on generation of bubbles that will project or “jet” the Pharmacologic agent at a controlled velocity into the acoustically disrupted thrombus to further de-polymerize the thrombus.
The apparatus described in U.S. Pat. No. 6,658,288 is designed for aiding thrombosis processes at a treatment site of a patient through the application of electric potential for repairing a blood vessel. The apparatus includes an elongated hollow prosthesis for placement within a blood vessel, said hollow prosthesis comprises an inner and outer surfaces, wherein an electric potential difference may be created between said surfaces.
An endovascular electrolytically detachable guidewire tip for the electroformation of thrombus in arteries is described in U.S. Pat. No. 5,122,136 and EP1329196. In these patent publications the guidewire used comprises a core wire having a distal portion susceptible to electrolytic disintegration in blood, where the distal portion is an exposed stainless steel segment comprising a coil connected at its proximate end to the core wire. In use, the distal tip of the guidewire is disposed in a vascular cavity and an electrical signal is applied to the distal tip to form a thrombus about the distal tip. The distal tip is then detached from the guidewire and left within the vascular cavity with the thrombus electrically formed thereabout.
U.S. Pat. No. 5,603,731 describes a method for preventing thrombosis by means of an expandable stent placed in a blood vessel and which act as a conductor on which electronegative potential is imposed by means of an electronegative generator implemented by a microwave detector diode incorporated in the stent structure. The microwave detector diode incorporated in the stent structure is designed to be operated from outside of the patient's body by the application of microwaves.
The methods described above have not yet provided satisfactory solutions for removal or dissolution of thrombus formation in blood vessels. Therefore there is a need for improved catheter designs and methods capable of removing thrombus from blood vessels or other body passages or organs.
It is therefore an object of the present invention to provide a method and apparatus for removal and/or dissolution of thrombus blood vessel by means of electrical fields.
It is another object of the present invention to provide a catheter device comprising electrodes designed for introduction into blood vessels or other body passages or organs for contacting and removing/retrieving a thrombus.
It is a further object of the present invention to provide procedures for introducing electrodes comprised in a catheter device into blood vessels or other body passages of a patient and applying electrical fields therein for removing thrombus material therefrom.
It is yet another object of the present invention to provide a method and catheter device for collecting blood clots and removing them from a blood vessel.
An additional object of the present invention is to provide a catheter device and methods for using it to open blocked body passages in a treated subject.
Other objects and advantages of the invention will become apparent as the description proceeds.